1 // SPDX-License-Identifier: GPL-2.0-only
5 * Copyright (C) 1991, 1992 Linus Torvalds
9 * 'fork.c' contains the help-routines for the 'fork' system call
10 * (see also entry.S and others).
11 * Fork is rather simple, once you get the hang of it, but the memory
12 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
15 #include <linux/anon_inodes.h>
16 #include <linux/slab.h>
17 #include <linux/sched/autogroup.h>
18 #include <linux/sched/mm.h>
19 #include <linux/sched/coredump.h>
20 #include <linux/sched/user.h>
21 #include <linux/sched/numa_balancing.h>
22 #include <linux/sched/stat.h>
23 #include <linux/sched/task.h>
24 #include <linux/sched/task_stack.h>
25 #include <linux/sched/cputime.h>
26 #include <linux/seq_file.h>
27 #include <linux/rtmutex.h>
28 #include <linux/init.h>
29 #include <linux/unistd.h>
30 #include <linux/module.h>
31 #include <linux/vmalloc.h>
32 #include <linux/completion.h>
33 #include <linux/personality.h>
34 #include <linux/mempolicy.h>
35 #include <linux/sem.h>
36 #include <linux/file.h>
37 #include <linux/fdtable.h>
38 #include <linux/iocontext.h>
39 #include <linux/key.h>
40 #include <linux/binfmts.h>
41 #include <linux/mman.h>
42 #include <linux/mmu_notifier.h>
45 #include <linux/mm_inline.h>
46 #include <linux/vmacache.h>
47 #include <linux/nsproxy.h>
48 #include <linux/capability.h>
49 #include <linux/cpu.h>
50 #include <linux/cgroup.h>
51 #include <linux/security.h>
52 #include <linux/hugetlb.h>
53 #include <linux/seccomp.h>
54 #include <linux/swap.h>
55 #include <linux/syscalls.h>
56 #include <linux/jiffies.h>
57 #include <linux/futex.h>
58 #include <linux/compat.h>
59 #include <linux/kthread.h>
60 #include <linux/task_io_accounting_ops.h>
61 #include <linux/rcupdate.h>
62 #include <linux/ptrace.h>
63 #include <linux/mount.h>
64 #include <linux/audit.h>
65 #include <linux/memcontrol.h>
66 #include <linux/ftrace.h>
67 #include <linux/proc_fs.h>
68 #include <linux/profile.h>
69 #include <linux/rmap.h>
70 #include <linux/ksm.h>
71 #include <linux/acct.h>
72 #include <linux/userfaultfd_k.h>
73 #include <linux/tsacct_kern.h>
74 #include <linux/cn_proc.h>
75 #include <linux/freezer.h>
76 #include <linux/delayacct.h>
77 #include <linux/taskstats_kern.h>
78 #include <linux/random.h>
79 #include <linux/tty.h>
80 #include <linux/fs_struct.h>
81 #include <linux/magic.h>
82 #include <linux/perf_event.h>
83 #include <linux/posix-timers.h>
84 #include <linux/user-return-notifier.h>
85 #include <linux/oom.h>
86 #include <linux/khugepaged.h>
87 #include <linux/signalfd.h>
88 #include <linux/uprobes.h>
89 #include <linux/aio.h>
90 #include <linux/compiler.h>
91 #include <linux/sysctl.h>
92 #include <linux/kcov.h>
93 #include <linux/livepatch.h>
94 #include <linux/thread_info.h>
95 #include <linux/stackleak.h>
96 #include <linux/kasan.h>
97 #include <linux/scs.h>
98 #include <linux/io_uring.h>
99 #include <linux/bpf.h>
100 #include <linux/sched/mm.h>
102 #include <asm/pgalloc.h>
103 #include <linux/uaccess.h>
104 #include <asm/mmu_context.h>
105 #include <asm/cacheflush.h>
106 #include <asm/tlbflush.h>
108 #include <trace/events/sched.h>
110 #define CREATE_TRACE_POINTS
111 #include <trace/events/task.h>
114 * Minimum number of threads to boot the kernel
116 #define MIN_THREADS 20
119 * Maximum number of threads
121 #define MAX_THREADS FUTEX_TID_MASK
124 * Protected counters by write_lock_irq(&tasklist_lock)
126 unsigned long total_forks; /* Handle normal Linux uptimes. */
127 int nr_threads; /* The idle threads do not count.. */
129 static int max_threads; /* tunable limit on nr_threads */
131 #define NAMED_ARRAY_INDEX(x) [x] = __stringify(x)
133 static const char * const resident_page_types[] = {
134 NAMED_ARRAY_INDEX(MM_FILEPAGES),
135 NAMED_ARRAY_INDEX(MM_ANONPAGES),
136 NAMED_ARRAY_INDEX(MM_SWAPENTS),
137 NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
140 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
142 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
144 #ifdef CONFIG_PROVE_RCU
145 int lockdep_tasklist_lock_is_held(void)
147 return lockdep_is_held(&tasklist_lock);
149 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
150 #endif /* #ifdef CONFIG_PROVE_RCU */
152 int nr_processes(void)
157 for_each_possible_cpu(cpu)
158 total += per_cpu(process_counts, cpu);
163 void __weak arch_release_task_struct(struct task_struct *tsk)
167 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
168 static struct kmem_cache *task_struct_cachep;
170 static inline struct task_struct *alloc_task_struct_node(int node)
172 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
175 static inline void free_task_struct(struct task_struct *tsk)
177 kmem_cache_free(task_struct_cachep, tsk);
181 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
184 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
185 * kmemcache based allocator.
187 # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
189 # ifdef CONFIG_VMAP_STACK
191 * vmalloc() is a bit slow, and calling vfree() enough times will force a TLB
192 * flush. Try to minimize the number of calls by caching stacks.
194 #define NR_CACHED_STACKS 2
195 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
199 struct vm_struct *stack_vm_area;
202 static bool try_release_thread_stack_to_cache(struct vm_struct *vm)
206 for (i = 0; i < NR_CACHED_STACKS; i++) {
207 if (this_cpu_cmpxchg(cached_stacks[i], NULL, vm) != NULL)
214 static void thread_stack_free_rcu(struct rcu_head *rh)
216 struct vm_stack *vm_stack = container_of(rh, struct vm_stack, rcu);
218 if (try_release_thread_stack_to_cache(vm_stack->stack_vm_area))
224 static void thread_stack_delayed_free(struct task_struct *tsk)
226 struct vm_stack *vm_stack = tsk->stack;
228 vm_stack->stack_vm_area = tsk->stack_vm_area;
229 call_rcu(&vm_stack->rcu, thread_stack_free_rcu);
232 static int free_vm_stack_cache(unsigned int cpu)
234 struct vm_struct **cached_vm_stacks = per_cpu_ptr(cached_stacks, cpu);
237 for (i = 0; i < NR_CACHED_STACKS; i++) {
238 struct vm_struct *vm_stack = cached_vm_stacks[i];
243 vfree(vm_stack->addr);
244 cached_vm_stacks[i] = NULL;
250 static int memcg_charge_kernel_stack(struct vm_struct *vm)
255 BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
256 BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
258 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
259 ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL, 0);
266 * If memcg_kmem_charge_page() fails, page's memory cgroup pointer is
267 * NULL, and memcg_kmem_uncharge_page() in free_thread_stack() will
270 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
271 memcg_kmem_uncharge_page(vm->pages[i], 0);
275 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
277 struct vm_struct *vm;
281 for (i = 0; i < NR_CACHED_STACKS; i++) {
284 s = this_cpu_xchg(cached_stacks[i], NULL);
289 /* Mark stack accessible for KASAN. */
290 kasan_unpoison_range(s->addr, THREAD_SIZE);
292 /* Clear stale pointers from reused stack. */
293 memset(s->addr, 0, THREAD_SIZE);
295 if (memcg_charge_kernel_stack(s)) {
300 tsk->stack_vm_area = s;
301 tsk->stack = s->addr;
306 * Allocated stacks are cached and later reused by new threads,
307 * so memcg accounting is performed manually on assigning/releasing
308 * stacks to tasks. Drop __GFP_ACCOUNT.
310 stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
311 VMALLOC_START, VMALLOC_END,
312 THREADINFO_GFP & ~__GFP_ACCOUNT,
314 0, node, __builtin_return_address(0));
318 vm = find_vm_area(stack);
319 if (memcg_charge_kernel_stack(vm)) {
324 * We can't call find_vm_area() in interrupt context, and
325 * free_thread_stack() can be called in interrupt context,
326 * so cache the vm_struct.
328 tsk->stack_vm_area = vm;
333 static void free_thread_stack(struct task_struct *tsk)
335 if (!try_release_thread_stack_to_cache(tsk->stack_vm_area))
336 thread_stack_delayed_free(tsk);
339 tsk->stack_vm_area = NULL;
342 # else /* !CONFIG_VMAP_STACK */
344 static void thread_stack_free_rcu(struct rcu_head *rh)
346 __free_pages(virt_to_page(rh), THREAD_SIZE_ORDER);
349 static void thread_stack_delayed_free(struct task_struct *tsk)
351 struct rcu_head *rh = tsk->stack;
353 call_rcu(rh, thread_stack_free_rcu);
356 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
358 struct page *page = alloc_pages_node(node, THREADINFO_GFP,
362 tsk->stack = kasan_reset_tag(page_address(page));
368 static void free_thread_stack(struct task_struct *tsk)
370 thread_stack_delayed_free(tsk);
374 # endif /* CONFIG_VMAP_STACK */
375 # else /* !(THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)) */
377 static struct kmem_cache *thread_stack_cache;
379 static void thread_stack_free_rcu(struct rcu_head *rh)
381 kmem_cache_free(thread_stack_cache, rh);
384 static void thread_stack_delayed_free(struct task_struct *tsk)
386 struct rcu_head *rh = tsk->stack;
388 call_rcu(rh, thread_stack_free_rcu);
391 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
393 unsigned long *stack;
394 stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
395 stack = kasan_reset_tag(stack);
397 return stack ? 0 : -ENOMEM;
400 static void free_thread_stack(struct task_struct *tsk)
402 thread_stack_delayed_free(tsk);
406 void thread_stack_cache_init(void)
408 thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
409 THREAD_SIZE, THREAD_SIZE, 0, 0,
411 BUG_ON(thread_stack_cache == NULL);
414 # endif /* THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) */
415 #else /* CONFIG_ARCH_THREAD_STACK_ALLOCATOR */
417 static int alloc_thread_stack_node(struct task_struct *tsk, int node)
419 unsigned long *stack;
421 stack = arch_alloc_thread_stack_node(tsk, node);
423 return stack ? 0 : -ENOMEM;
426 static void free_thread_stack(struct task_struct *tsk)
428 arch_free_thread_stack(tsk);
432 #endif /* !CONFIG_ARCH_THREAD_STACK_ALLOCATOR */
434 /* SLAB cache for signal_struct structures (tsk->signal) */
435 static struct kmem_cache *signal_cachep;
437 /* SLAB cache for sighand_struct structures (tsk->sighand) */
438 struct kmem_cache *sighand_cachep;
440 /* SLAB cache for files_struct structures (tsk->files) */
441 struct kmem_cache *files_cachep;
443 /* SLAB cache for fs_struct structures (tsk->fs) */
444 struct kmem_cache *fs_cachep;
446 /* SLAB cache for vm_area_struct structures */
447 static struct kmem_cache *vm_area_cachep;
449 /* SLAB cache for mm_struct structures (tsk->mm) */
450 static struct kmem_cache *mm_cachep;
452 struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
454 struct vm_area_struct *vma;
456 vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
462 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
464 struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
467 ASSERT_EXCLUSIVE_WRITER(orig->vm_flags);
468 ASSERT_EXCLUSIVE_WRITER(orig->vm_file);
470 * orig->shared.rb may be modified concurrently, but the clone
471 * will be reinitialized.
473 *new = data_race(*orig);
474 INIT_LIST_HEAD(&new->anon_vma_chain);
475 new->vm_next = new->vm_prev = NULL;
476 dup_anon_vma_name(orig, new);
481 void vm_area_free(struct vm_area_struct *vma)
483 free_anon_vma_name(vma);
484 kmem_cache_free(vm_area_cachep, vma);
487 static void account_kernel_stack(struct task_struct *tsk, int account)
489 if (IS_ENABLED(CONFIG_VMAP_STACK)) {
490 struct vm_struct *vm = task_stack_vm_area(tsk);
493 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
494 mod_lruvec_page_state(vm->pages[i], NR_KERNEL_STACK_KB,
495 account * (PAGE_SIZE / 1024));
497 void *stack = task_stack_page(tsk);
499 /* All stack pages are in the same node. */
500 mod_lruvec_kmem_state(stack, NR_KERNEL_STACK_KB,
501 account * (THREAD_SIZE / 1024));
505 void exit_task_stack_account(struct task_struct *tsk)
507 account_kernel_stack(tsk, -1);
509 if (IS_ENABLED(CONFIG_VMAP_STACK)) {
510 struct vm_struct *vm;
513 vm = task_stack_vm_area(tsk);
514 for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
515 memcg_kmem_uncharge_page(vm->pages[i], 0);
519 static void release_task_stack(struct task_struct *tsk)
521 if (WARN_ON(READ_ONCE(tsk->__state) != TASK_DEAD))
522 return; /* Better to leak the stack than to free prematurely */
524 free_thread_stack(tsk);
527 #ifdef CONFIG_THREAD_INFO_IN_TASK
528 void put_task_stack(struct task_struct *tsk)
530 if (refcount_dec_and_test(&tsk->stack_refcount))
531 release_task_stack(tsk);
535 void free_task(struct task_struct *tsk)
537 release_user_cpus_ptr(tsk);
540 #ifndef CONFIG_THREAD_INFO_IN_TASK
542 * The task is finally done with both the stack and thread_info,
545 release_task_stack(tsk);
548 * If the task had a separate stack allocation, it should be gone
551 WARN_ON_ONCE(refcount_read(&tsk->stack_refcount) != 0);
553 rt_mutex_debug_task_free(tsk);
554 ftrace_graph_exit_task(tsk);
555 arch_release_task_struct(tsk);
556 if (tsk->flags & PF_KTHREAD)
557 free_kthread_struct(tsk);
558 free_task_struct(tsk);
560 EXPORT_SYMBOL(free_task);
562 static void dup_mm_exe_file(struct mm_struct *mm, struct mm_struct *oldmm)
564 struct file *exe_file;
566 exe_file = get_mm_exe_file(oldmm);
567 RCU_INIT_POINTER(mm->exe_file, exe_file);
569 * We depend on the oldmm having properly denied write access to the
572 if (exe_file && deny_write_access(exe_file))
573 pr_warn_once("deny_write_access() failed in %s\n", __func__);
577 static __latent_entropy int dup_mmap(struct mm_struct *mm,
578 struct mm_struct *oldmm)
580 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
581 struct rb_node **rb_link, *rb_parent;
583 unsigned long charge;
586 uprobe_start_dup_mmap();
587 if (mmap_write_lock_killable(oldmm)) {
589 goto fail_uprobe_end;
591 flush_cache_dup_mm(oldmm);
592 uprobe_dup_mmap(oldmm, mm);
594 * Not linked in yet - no deadlock potential:
596 mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING);
598 /* No ordering required: file already has been exposed. */
599 dup_mm_exe_file(mm, oldmm);
601 mm->total_vm = oldmm->total_vm;
602 mm->data_vm = oldmm->data_vm;
603 mm->exec_vm = oldmm->exec_vm;
604 mm->stack_vm = oldmm->stack_vm;
606 rb_link = &mm->mm_rb.rb_node;
609 retval = ksm_fork(mm, oldmm);
612 retval = khugepaged_fork(mm, oldmm);
617 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
620 if (mpnt->vm_flags & VM_DONTCOPY) {
621 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt));
626 * Don't duplicate many vmas if we've been oom-killed (for
629 if (fatal_signal_pending(current)) {
633 if (mpnt->vm_flags & VM_ACCOUNT) {
634 unsigned long len = vma_pages(mpnt);
636 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
640 tmp = vm_area_dup(mpnt);
643 retval = vma_dup_policy(mpnt, tmp);
645 goto fail_nomem_policy;
647 retval = dup_userfaultfd(tmp, &uf);
649 goto fail_nomem_anon_vma_fork;
650 if (tmp->vm_flags & VM_WIPEONFORK) {
652 * VM_WIPEONFORK gets a clean slate in the child.
653 * Don't prepare anon_vma until fault since we don't
654 * copy page for current vma.
656 tmp->anon_vma = NULL;
657 } else if (anon_vma_fork(tmp, mpnt))
658 goto fail_nomem_anon_vma_fork;
659 tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
662 struct address_space *mapping = file->f_mapping;
665 i_mmap_lock_write(mapping);
666 if (tmp->vm_flags & VM_SHARED)
667 mapping_allow_writable(mapping);
668 flush_dcache_mmap_lock(mapping);
669 /* insert tmp into the share list, just after mpnt */
670 vma_interval_tree_insert_after(tmp, mpnt,
672 flush_dcache_mmap_unlock(mapping);
673 i_mmap_unlock_write(mapping);
677 * Clear hugetlb-related page reserves for children. This only
678 * affects MAP_PRIVATE mappings. Faults generated by the child
679 * are not guaranteed to succeed, even if read-only
681 if (is_vm_hugetlb_page(tmp))
682 reset_vma_resv_huge_pages(tmp);
685 * Link in the new vma and copy the page table entries.
688 pprev = &tmp->vm_next;
692 __vma_link_rb(mm, tmp, rb_link, rb_parent);
693 rb_link = &tmp->vm_rb.rb_right;
694 rb_parent = &tmp->vm_rb;
697 if (!(tmp->vm_flags & VM_WIPEONFORK))
698 retval = copy_page_range(tmp, mpnt);
700 if (tmp->vm_ops && tmp->vm_ops->open)
701 tmp->vm_ops->open(tmp);
706 /* a new mm has just been created */
707 retval = arch_dup_mmap(oldmm, mm);
709 mmap_write_unlock(mm);
711 mmap_write_unlock(oldmm);
712 dup_userfaultfd_complete(&uf);
714 uprobe_end_dup_mmap();
716 fail_nomem_anon_vma_fork:
717 mpol_put(vma_policy(tmp));
722 vm_unacct_memory(charge);
726 static inline int mm_alloc_pgd(struct mm_struct *mm)
728 mm->pgd = pgd_alloc(mm);
729 if (unlikely(!mm->pgd))
734 static inline void mm_free_pgd(struct mm_struct *mm)
736 pgd_free(mm, mm->pgd);
739 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
741 mmap_write_lock(oldmm);
742 dup_mm_exe_file(mm, oldmm);
743 mmap_write_unlock(oldmm);
746 #define mm_alloc_pgd(mm) (0)
747 #define mm_free_pgd(mm)
748 #endif /* CONFIG_MMU */
750 static void check_mm(struct mm_struct *mm)
754 BUILD_BUG_ON_MSG(ARRAY_SIZE(resident_page_types) != NR_MM_COUNTERS,
755 "Please make sure 'struct resident_page_types[]' is updated as well");
757 for (i = 0; i < NR_MM_COUNTERS; i++) {
758 long x = atomic_long_read(&mm->rss_stat.count[i]);
761 pr_alert("BUG: Bad rss-counter state mm:%p type:%s val:%ld\n",
762 mm, resident_page_types[i], x);
765 if (mm_pgtables_bytes(mm))
766 pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n",
767 mm_pgtables_bytes(mm));
769 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
770 VM_BUG_ON_MM(mm->pmd_huge_pte, mm);
774 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
775 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
778 * Called when the last reference to the mm
779 * is dropped: either by a lazy thread or by
780 * mmput. Free the page directory and the mm.
782 void __mmdrop(struct mm_struct *mm)
784 BUG_ON(mm == &init_mm);
785 WARN_ON_ONCE(mm == current->mm);
786 WARN_ON_ONCE(mm == current->active_mm);
789 mmu_notifier_subscriptions_destroy(mm);
791 put_user_ns(mm->user_ns);
794 EXPORT_SYMBOL_GPL(__mmdrop);
796 static void mmdrop_async_fn(struct work_struct *work)
798 struct mm_struct *mm;
800 mm = container_of(work, struct mm_struct, async_put_work);
804 static void mmdrop_async(struct mm_struct *mm)
806 if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
807 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
808 schedule_work(&mm->async_put_work);
812 static inline void free_signal_struct(struct signal_struct *sig)
814 taskstats_tgid_free(sig);
815 sched_autogroup_exit(sig);
817 * __mmdrop is not safe to call from softirq context on x86 due to
818 * pgd_dtor so postpone it to the async context
821 mmdrop_async(sig->oom_mm);
822 kmem_cache_free(signal_cachep, sig);
825 static inline void put_signal_struct(struct signal_struct *sig)
827 if (refcount_dec_and_test(&sig->sigcnt))
828 free_signal_struct(sig);
831 void __put_task_struct(struct task_struct *tsk)
833 WARN_ON(!tsk->exit_state);
834 WARN_ON(refcount_read(&tsk->usage));
835 WARN_ON(tsk == current);
839 task_numa_free(tsk, true);
840 security_task_free(tsk);
841 bpf_task_storage_free(tsk);
843 delayacct_tsk_free(tsk);
844 put_signal_struct(tsk->signal);
845 sched_core_free(tsk);
848 EXPORT_SYMBOL_GPL(__put_task_struct);
850 void __init __weak arch_task_cache_init(void) { }
855 static void set_max_threads(unsigned int max_threads_suggested)
858 unsigned long nr_pages = totalram_pages();
861 * The number of threads shall be limited such that the thread
862 * structures may only consume a small part of the available memory.
864 if (fls64(nr_pages) + fls64(PAGE_SIZE) > 64)
865 threads = MAX_THREADS;
867 threads = div64_u64((u64) nr_pages * (u64) PAGE_SIZE,
868 (u64) THREAD_SIZE * 8UL);
870 if (threads > max_threads_suggested)
871 threads = max_threads_suggested;
873 max_threads = clamp_t(u64, threads, MIN_THREADS, MAX_THREADS);
876 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
877 /* Initialized by the architecture: */
878 int arch_task_struct_size __read_mostly;
881 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
882 static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
884 /* Fetch thread_struct whitelist for the architecture. */
885 arch_thread_struct_whitelist(offset, size);
888 * Handle zero-sized whitelist or empty thread_struct, otherwise
889 * adjust offset to position of thread_struct in task_struct.
891 if (unlikely(*size == 0))
894 *offset += offsetof(struct task_struct, thread);
896 #endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */
898 void __init fork_init(void)
901 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
902 #ifndef ARCH_MIN_TASKALIGN
903 #define ARCH_MIN_TASKALIGN 0
905 int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
906 unsigned long useroffset, usersize;
908 /* create a slab on which task_structs can be allocated */
909 task_struct_whitelist(&useroffset, &usersize);
910 task_struct_cachep = kmem_cache_create_usercopy("task_struct",
911 arch_task_struct_size, align,
912 SLAB_PANIC|SLAB_ACCOUNT,
913 useroffset, usersize, NULL);
916 /* do the arch specific task caches init */
917 arch_task_cache_init();
919 set_max_threads(MAX_THREADS);
921 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
922 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
923 init_task.signal->rlim[RLIMIT_SIGPENDING] =
924 init_task.signal->rlim[RLIMIT_NPROC];
926 for (i = 0; i < MAX_PER_NAMESPACE_UCOUNTS; i++)
927 init_user_ns.ucount_max[i] = max_threads/2;
929 set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_NPROC, RLIM_INFINITY);
930 set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, RLIM_INFINITY);
931 set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_SIGPENDING, RLIM_INFINITY);
932 set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MEMLOCK, RLIM_INFINITY);
934 #ifdef CONFIG_VMAP_STACK
935 cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",
936 NULL, free_vm_stack_cache);
941 lockdep_init_task(&init_task);
945 int __weak arch_dup_task_struct(struct task_struct *dst,
946 struct task_struct *src)
952 void set_task_stack_end_magic(struct task_struct *tsk)
954 unsigned long *stackend;
956 stackend = end_of_stack(tsk);
957 *stackend = STACK_END_MAGIC; /* for overflow detection */
960 static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
962 struct task_struct *tsk;
965 if (node == NUMA_NO_NODE)
966 node = tsk_fork_get_node(orig);
967 tsk = alloc_task_struct_node(node);
971 err = arch_dup_task_struct(tsk, orig);
975 err = alloc_thread_stack_node(tsk, node);
979 #ifdef CONFIG_THREAD_INFO_IN_TASK
980 refcount_set(&tsk->stack_refcount, 1);
982 account_kernel_stack(tsk, 1);
984 err = scs_prepare(tsk, node);
988 #ifdef CONFIG_SECCOMP
990 * We must handle setting up seccomp filters once we're under
991 * the sighand lock in case orig has changed between now and
992 * then. Until then, filter must be NULL to avoid messing up
993 * the usage counts on the error path calling free_task.
995 tsk->seccomp.filter = NULL;
998 setup_thread_stack(tsk, orig);
999 clear_user_return_notifier(tsk);
1000 clear_tsk_need_resched(tsk);
1001 set_task_stack_end_magic(tsk);
1002 clear_syscall_work_syscall_user_dispatch(tsk);
1004 #ifdef CONFIG_STACKPROTECTOR
1005 tsk->stack_canary = get_random_canary();
1007 if (orig->cpus_ptr == &orig->cpus_mask)
1008 tsk->cpus_ptr = &tsk->cpus_mask;
1009 dup_user_cpus_ptr(tsk, orig, node);
1012 * One for the user space visible state that goes away when reaped.
1013 * One for the scheduler.
1015 refcount_set(&tsk->rcu_users, 2);
1016 /* One for the rcu users */
1017 refcount_set(&tsk->usage, 1);
1018 #ifdef CONFIG_BLK_DEV_IO_TRACE
1019 tsk->btrace_seq = 0;
1021 tsk->splice_pipe = NULL;
1022 tsk->task_frag.page = NULL;
1023 tsk->wake_q.next = NULL;
1024 tsk->worker_private = NULL;
1026 kcov_task_init(tsk);
1027 kmap_local_fork(tsk);
1029 #ifdef CONFIG_FAULT_INJECTION
1033 #ifdef CONFIG_BLK_CGROUP
1034 tsk->throttle_queue = NULL;
1035 tsk->use_memdelay = 0;
1038 #ifdef CONFIG_IOMMU_SVA
1039 tsk->pasid_activated = 0;
1043 tsk->active_memcg = NULL;
1048 exit_task_stack_account(tsk);
1049 free_thread_stack(tsk);
1051 free_task_struct(tsk);
1055 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
1057 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
1059 static int __init coredump_filter_setup(char *s)
1061 default_dump_filter =
1062 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
1063 MMF_DUMP_FILTER_MASK;
1067 __setup("coredump_filter=", coredump_filter_setup);
1069 #include <linux/init_task.h>
1071 static void mm_init_aio(struct mm_struct *mm)
1074 spin_lock_init(&mm->ioctx_lock);
1075 mm->ioctx_table = NULL;
1079 static __always_inline void mm_clear_owner(struct mm_struct *mm,
1080 struct task_struct *p)
1084 WRITE_ONCE(mm->owner, NULL);
1088 static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1095 static void mm_init_uprobes_state(struct mm_struct *mm)
1097 #ifdef CONFIG_UPROBES
1098 mm->uprobes_state.xol_area = NULL;
1102 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
1103 struct user_namespace *user_ns)
1106 mm->mm_rb = RB_ROOT;
1107 mm->vmacache_seqnum = 0;
1108 atomic_set(&mm->mm_users, 1);
1109 atomic_set(&mm->mm_count, 1);
1110 seqcount_init(&mm->write_protect_seq);
1112 INIT_LIST_HEAD(&mm->mmlist);
1113 mm_pgtables_bytes_init(mm);
1116 atomic64_set(&mm->pinned_vm, 0);
1117 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
1118 spin_lock_init(&mm->page_table_lock);
1119 spin_lock_init(&mm->arg_lock);
1120 mm_init_cpumask(mm);
1122 mm_init_owner(mm, p);
1124 RCU_INIT_POINTER(mm->exe_file, NULL);
1125 mmu_notifier_subscriptions_init(mm);
1126 init_tlb_flush_pending(mm);
1127 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
1128 mm->pmd_huge_pte = NULL;
1130 mm_init_uprobes_state(mm);
1131 hugetlb_count_init(mm);
1134 mm->flags = current->mm->flags & MMF_INIT_MASK;
1135 mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
1137 mm->flags = default_dump_filter;
1141 if (mm_alloc_pgd(mm))
1144 if (init_new_context(p, mm))
1145 goto fail_nocontext;
1147 mm->user_ns = get_user_ns(user_ns);
1158 * Allocate and initialize an mm_struct.
1160 struct mm_struct *mm_alloc(void)
1162 struct mm_struct *mm;
1168 memset(mm, 0, sizeof(*mm));
1169 return mm_init(mm, current, current_user_ns());
1172 static inline void __mmput(struct mm_struct *mm)
1174 VM_BUG_ON(atomic_read(&mm->mm_users));
1176 uprobe_clear_state(mm);
1179 khugepaged_exit(mm); /* must run before exit_mmap */
1181 mm_put_huge_zero_page(mm);
1182 set_mm_exe_file(mm, NULL);
1183 if (!list_empty(&mm->mmlist)) {
1184 spin_lock(&mmlist_lock);
1185 list_del(&mm->mmlist);
1186 spin_unlock(&mmlist_lock);
1189 module_put(mm->binfmt->module);
1195 * Decrement the use count and release all resources for an mm.
1197 void mmput(struct mm_struct *mm)
1201 if (atomic_dec_and_test(&mm->mm_users))
1204 EXPORT_SYMBOL_GPL(mmput);
1207 static void mmput_async_fn(struct work_struct *work)
1209 struct mm_struct *mm = container_of(work, struct mm_struct,
1215 void mmput_async(struct mm_struct *mm)
1217 if (atomic_dec_and_test(&mm->mm_users)) {
1218 INIT_WORK(&mm->async_put_work, mmput_async_fn);
1219 schedule_work(&mm->async_put_work);
1225 * set_mm_exe_file - change a reference to the mm's executable file
1227 * This changes mm's executable file (shown as symlink /proc/[pid]/exe).
1229 * Main users are mmput() and sys_execve(). Callers prevent concurrent
1230 * invocations: in mmput() nobody alive left, in execve task is single
1233 * Can only fail if new_exe_file != NULL.
1235 int set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1237 struct file *old_exe_file;
1240 * It is safe to dereference the exe_file without RCU as
1241 * this function is only called if nobody else can access
1242 * this mm -- see comment above for justification.
1244 old_exe_file = rcu_dereference_raw(mm->exe_file);
1248 * We expect the caller (i.e., sys_execve) to already denied
1249 * write access, so this is unlikely to fail.
1251 if (unlikely(deny_write_access(new_exe_file)))
1253 get_file(new_exe_file);
1255 rcu_assign_pointer(mm->exe_file, new_exe_file);
1257 allow_write_access(old_exe_file);
1264 * replace_mm_exe_file - replace a reference to the mm's executable file
1266 * This changes mm's executable file (shown as symlink /proc/[pid]/exe),
1267 * dealing with concurrent invocation and without grabbing the mmap lock in
1270 * Main user is sys_prctl(PR_SET_MM_MAP/EXE_FILE).
1272 int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
1274 struct vm_area_struct *vma;
1275 struct file *old_exe_file;
1278 /* Forbid mm->exe_file change if old file still mapped. */
1279 old_exe_file = get_mm_exe_file(mm);
1282 for (vma = mm->mmap; vma && !ret; vma = vma->vm_next) {
1285 if (path_equal(&vma->vm_file->f_path,
1286 &old_exe_file->f_path))
1289 mmap_read_unlock(mm);
1295 /* set the new file, lockless */
1296 ret = deny_write_access(new_exe_file);
1299 get_file(new_exe_file);
1301 old_exe_file = xchg(&mm->exe_file, new_exe_file);
1304 * Don't race with dup_mmap() getting the file and disallowing
1305 * write access while someone might open the file writable.
1308 allow_write_access(old_exe_file);
1310 mmap_read_unlock(mm);
1316 * get_mm_exe_file - acquire a reference to the mm's executable file
1318 * Returns %NULL if mm has no associated executable file.
1319 * User must release file via fput().
1321 struct file *get_mm_exe_file(struct mm_struct *mm)
1323 struct file *exe_file;
1326 exe_file = rcu_dereference(mm->exe_file);
1327 if (exe_file && !get_file_rcu(exe_file))
1334 * get_task_exe_file - acquire a reference to the task's executable file
1336 * Returns %NULL if task's mm (if any) has no associated executable file or
1337 * this is a kernel thread with borrowed mm (see the comment above get_task_mm).
1338 * User must release file via fput().
1340 struct file *get_task_exe_file(struct task_struct *task)
1342 struct file *exe_file = NULL;
1343 struct mm_struct *mm;
1348 if (!(task->flags & PF_KTHREAD))
1349 exe_file = get_mm_exe_file(mm);
1356 * get_task_mm - acquire a reference to the task's mm
1358 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
1359 * this kernel workthread has transiently adopted a user mm with use_mm,
1360 * to do its AIO) is not set and if so returns a reference to it, after
1361 * bumping up the use count. User must release the mm via mmput()
1362 * after use. Typically used by /proc and ptrace.
1364 struct mm_struct *get_task_mm(struct task_struct *task)
1366 struct mm_struct *mm;
1371 if (task->flags & PF_KTHREAD)
1379 EXPORT_SYMBOL_GPL(get_task_mm);
1381 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
1383 struct mm_struct *mm;
1386 err = down_read_killable(&task->signal->exec_update_lock);
1388 return ERR_PTR(err);
1390 mm = get_task_mm(task);
1391 if (mm && mm != current->mm &&
1392 !ptrace_may_access(task, mode)) {
1394 mm = ERR_PTR(-EACCES);
1396 up_read(&task->signal->exec_update_lock);
1401 static void complete_vfork_done(struct task_struct *tsk)
1403 struct completion *vfork;
1406 vfork = tsk->vfork_done;
1407 if (likely(vfork)) {
1408 tsk->vfork_done = NULL;
1414 static int wait_for_vfork_done(struct task_struct *child,
1415 struct completion *vfork)
1419 freezer_do_not_count();
1420 cgroup_enter_frozen();
1421 killed = wait_for_completion_killable(vfork);
1422 cgroup_leave_frozen(false);
1427 child->vfork_done = NULL;
1431 put_task_struct(child);
1435 /* Please note the differences between mmput and mm_release.
1436 * mmput is called whenever we stop holding onto a mm_struct,
1437 * error success whatever.
1439 * mm_release is called after a mm_struct has been removed
1440 * from the current process.
1442 * This difference is important for error handling, when we
1443 * only half set up a mm_struct for a new process and need to restore
1444 * the old one. Because we mmput the new mm_struct before
1445 * restoring the old one. . .
1446 * Eric Biederman 10 January 1998
1448 static void mm_release(struct task_struct *tsk, struct mm_struct *mm)
1450 uprobe_free_utask(tsk);
1452 /* Get rid of any cached register state */
1453 deactivate_mm(tsk, mm);
1456 * Signal userspace if we're not exiting with a core dump
1457 * because we want to leave the value intact for debugging
1460 if (tsk->clear_child_tid) {
1461 if (atomic_read(&mm->mm_users) > 1) {
1463 * We don't check the error code - if userspace has
1464 * not set up a proper pointer then tough luck.
1466 put_user(0, tsk->clear_child_tid);
1467 do_futex(tsk->clear_child_tid, FUTEX_WAKE,
1468 1, NULL, NULL, 0, 0);
1470 tsk->clear_child_tid = NULL;
1474 * All done, finally we can wake up parent and return this mm to him.
1475 * Also kthread_stop() uses this completion for synchronization.
1477 if (tsk->vfork_done)
1478 complete_vfork_done(tsk);
1481 void exit_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1483 futex_exit_release(tsk);
1484 mm_release(tsk, mm);
1487 void exec_mm_release(struct task_struct *tsk, struct mm_struct *mm)
1489 futex_exec_release(tsk);
1490 mm_release(tsk, mm);
1494 * dup_mm() - duplicates an existing mm structure
1495 * @tsk: the task_struct with which the new mm will be associated.
1496 * @oldmm: the mm to duplicate.
1498 * Allocates a new mm structure and duplicates the provided @oldmm structure
1501 * Return: the duplicated mm or NULL on failure.
1503 static struct mm_struct *dup_mm(struct task_struct *tsk,
1504 struct mm_struct *oldmm)
1506 struct mm_struct *mm;
1513 memcpy(mm, oldmm, sizeof(*mm));
1515 if (!mm_init(mm, tsk, mm->user_ns))
1518 err = dup_mmap(mm, oldmm);
1522 mm->hiwater_rss = get_mm_rss(mm);
1523 mm->hiwater_vm = mm->total_vm;
1525 if (mm->binfmt && !try_module_get(mm->binfmt->module))
1531 /* don't put binfmt in mmput, we haven't got module yet */
1533 mm_init_owner(mm, NULL);
1540 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
1542 struct mm_struct *mm, *oldmm;
1544 tsk->min_flt = tsk->maj_flt = 0;
1545 tsk->nvcsw = tsk->nivcsw = 0;
1546 #ifdef CONFIG_DETECT_HUNG_TASK
1547 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
1548 tsk->last_switch_time = 0;
1552 tsk->active_mm = NULL;
1555 * Are we cloning a kernel thread?
1557 * We need to steal a active VM for that..
1559 oldmm = current->mm;
1563 /* initialize the new vmacache entries */
1564 vmacache_flush(tsk);
1566 if (clone_flags & CLONE_VM) {
1570 mm = dup_mm(tsk, current->mm);
1576 tsk->active_mm = mm;
1580 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
1582 struct fs_struct *fs = current->fs;
1583 if (clone_flags & CLONE_FS) {
1584 /* tsk->fs is already what we want */
1585 spin_lock(&fs->lock);
1587 spin_unlock(&fs->lock);
1591 spin_unlock(&fs->lock);
1594 tsk->fs = copy_fs_struct(fs);
1600 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
1602 struct files_struct *oldf, *newf;
1606 * A background process may not have any files ...
1608 oldf = current->files;
1612 if (clone_flags & CLONE_FILES) {
1613 atomic_inc(&oldf->count);
1617 newf = dup_fd(oldf, NR_OPEN_MAX, &error);
1627 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1629 struct sighand_struct *sig;
1631 if (clone_flags & CLONE_SIGHAND) {
1632 refcount_inc(¤t->sighand->count);
1635 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1636 RCU_INIT_POINTER(tsk->sighand, sig);
1640 refcount_set(&sig->count, 1);
1641 spin_lock_irq(¤t->sighand->siglock);
1642 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1643 spin_unlock_irq(¤t->sighand->siglock);
1645 /* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
1646 if (clone_flags & CLONE_CLEAR_SIGHAND)
1647 flush_signal_handlers(tsk, 0);
1652 void __cleanup_sighand(struct sighand_struct *sighand)
1654 if (refcount_dec_and_test(&sighand->count)) {
1655 signalfd_cleanup(sighand);
1657 * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it
1658 * without an RCU grace period, see __lock_task_sighand().
1660 kmem_cache_free(sighand_cachep, sighand);
1665 * Initialize POSIX timer handling for a thread group.
1667 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1669 struct posix_cputimers *pct = &sig->posix_cputimers;
1670 unsigned long cpu_limit;
1672 cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1673 posix_cputimers_group_init(pct, cpu_limit);
1676 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1678 struct signal_struct *sig;
1680 if (clone_flags & CLONE_THREAD)
1683 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1688 sig->nr_threads = 1;
1689 atomic_set(&sig->live, 1);
1690 refcount_set(&sig->sigcnt, 1);
1692 /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */
1693 sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node);
1694 tsk->thread_node = (struct list_head)LIST_HEAD_INIT(sig->thread_head);
1696 init_waitqueue_head(&sig->wait_chldexit);
1697 sig->curr_target = tsk;
1698 init_sigpending(&sig->shared_pending);
1699 INIT_HLIST_HEAD(&sig->multiprocess);
1700 seqlock_init(&sig->stats_lock);
1701 prev_cputime_init(&sig->prev_cputime);
1703 #ifdef CONFIG_POSIX_TIMERS
1704 INIT_LIST_HEAD(&sig->posix_timers);
1705 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1706 sig->real_timer.function = it_real_fn;
1709 task_lock(current->group_leader);
1710 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1711 task_unlock(current->group_leader);
1713 posix_cpu_timers_init_group(sig);
1715 tty_audit_fork(sig);
1716 sched_autogroup_fork(sig);
1718 sig->oom_score_adj = current->signal->oom_score_adj;
1719 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1721 mutex_init(&sig->cred_guard_mutex);
1722 init_rwsem(&sig->exec_update_lock);
1727 static void copy_seccomp(struct task_struct *p)
1729 #ifdef CONFIG_SECCOMP
1731 * Must be called with sighand->lock held, which is common to
1732 * all threads in the group. Holding cred_guard_mutex is not
1733 * needed because this new task is not yet running and cannot
1736 assert_spin_locked(¤t->sighand->siglock);
1738 /* Ref-count the new filter user, and assign it. */
1739 get_seccomp_filter(current);
1740 p->seccomp = current->seccomp;
1743 * Explicitly enable no_new_privs here in case it got set
1744 * between the task_struct being duplicated and holding the
1745 * sighand lock. The seccomp state and nnp must be in sync.
1747 if (task_no_new_privs(current))
1748 task_set_no_new_privs(p);
1751 * If the parent gained a seccomp mode after copying thread
1752 * flags and between before we held the sighand lock, we have
1753 * to manually enable the seccomp thread flag here.
1755 if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
1756 set_task_syscall_work(p, SECCOMP);
1760 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1762 current->clear_child_tid = tidptr;
1764 return task_pid_vnr(current);
1767 static void rt_mutex_init_task(struct task_struct *p)
1769 raw_spin_lock_init(&p->pi_lock);
1770 #ifdef CONFIG_RT_MUTEXES
1771 p->pi_waiters = RB_ROOT_CACHED;
1772 p->pi_top_task = NULL;
1773 p->pi_blocked_on = NULL;
1777 static inline void init_task_pid_links(struct task_struct *task)
1781 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type)
1782 INIT_HLIST_NODE(&task->pid_links[type]);
1786 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1788 if (type == PIDTYPE_PID)
1789 task->thread_pid = pid;
1791 task->signal->pids[type] = pid;
1794 static inline void rcu_copy_process(struct task_struct *p)
1796 #ifdef CONFIG_PREEMPT_RCU
1797 p->rcu_read_lock_nesting = 0;
1798 p->rcu_read_unlock_special.s = 0;
1799 p->rcu_blocked_node = NULL;
1800 INIT_LIST_HEAD(&p->rcu_node_entry);
1801 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1802 #ifdef CONFIG_TASKS_RCU
1803 p->rcu_tasks_holdout = false;
1804 INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
1805 p->rcu_tasks_idle_cpu = -1;
1806 #endif /* #ifdef CONFIG_TASKS_RCU */
1807 #ifdef CONFIG_TASKS_TRACE_RCU
1808 p->trc_reader_nesting = 0;
1809 p->trc_reader_special.s = 0;
1810 INIT_LIST_HEAD(&p->trc_holdout_list);
1811 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
1814 struct pid *pidfd_pid(const struct file *file)
1816 if (file->f_op == &pidfd_fops)
1817 return file->private_data;
1819 return ERR_PTR(-EBADF);
1822 static int pidfd_release(struct inode *inode, struct file *file)
1824 struct pid *pid = file->private_data;
1826 file->private_data = NULL;
1831 #ifdef CONFIG_PROC_FS
1833 * pidfd_show_fdinfo - print information about a pidfd
1834 * @m: proc fdinfo file
1835 * @f: file referencing a pidfd
1838 * This function will print the pid that a given pidfd refers to in the
1839 * pid namespace of the procfs instance.
1840 * If the pid namespace of the process is not a descendant of the pid
1841 * namespace of the procfs instance 0 will be shown as its pid. This is
1842 * similar to calling getppid() on a process whose parent is outside of
1843 * its pid namespace.
1846 * If pid namespaces are supported then this function will also print
1847 * the pid of a given pidfd refers to for all descendant pid namespaces
1848 * starting from the current pid namespace of the instance, i.e. the
1849 * Pid field and the first entry in the NSpid field will be identical.
1850 * If the pid namespace of the process is not a descendant of the pid
1851 * namespace of the procfs instance 0 will be shown as its first NSpid
1852 * entry and no others will be shown.
1853 * Note that this differs from the Pid and NSpid fields in
1854 * /proc/<pid>/status where Pid and NSpid are always shown relative to
1855 * the pid namespace of the procfs instance. The difference becomes
1856 * obvious when sending around a pidfd between pid namespaces from a
1857 * different branch of the tree, i.e. where no ancestral relation is
1858 * present between the pid namespaces:
1859 * - create two new pid namespaces ns1 and ns2 in the initial pid
1860 * namespace (also take care to create new mount namespaces in the
1861 * new pid namespace and mount procfs)
1862 * - create a process with a pidfd in ns1
1863 * - send pidfd from ns1 to ns2
1864 * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid
1865 * have exactly one entry, which is 0
1867 static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
1869 struct pid *pid = f->private_data;
1870 struct pid_namespace *ns;
1873 if (likely(pid_has_task(pid, PIDTYPE_PID))) {
1874 ns = proc_pid_ns(file_inode(m->file)->i_sb);
1875 nr = pid_nr_ns(pid, ns);
1878 seq_put_decimal_ll(m, "Pid:\t", nr);
1880 #ifdef CONFIG_PID_NS
1881 seq_put_decimal_ll(m, "\nNSpid:\t", nr);
1885 /* If nr is non-zero it means that 'pid' is valid and that
1886 * ns, i.e. the pid namespace associated with the procfs
1887 * instance, is in the pid namespace hierarchy of pid.
1888 * Start at one below the already printed level.
1890 for (i = ns->level + 1; i <= pid->level; i++)
1891 seq_put_decimal_ll(m, "\t", pid->numbers[i].nr);
1899 * Poll support for process exit notification.
1901 static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
1903 struct pid *pid = file->private_data;
1904 __poll_t poll_flags = 0;
1906 poll_wait(file, &pid->wait_pidfd, pts);
1909 * Inform pollers only when the whole thread group exits.
1910 * If the thread group leader exits before all other threads in the
1911 * group, then poll(2) should block, similar to the wait(2) family.
1913 if (thread_group_exited(pid))
1914 poll_flags = EPOLLIN | EPOLLRDNORM;
1919 const struct file_operations pidfd_fops = {
1920 .release = pidfd_release,
1922 #ifdef CONFIG_PROC_FS
1923 .show_fdinfo = pidfd_show_fdinfo,
1927 static void __delayed_free_task(struct rcu_head *rhp)
1929 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
1934 static __always_inline void delayed_free_task(struct task_struct *tsk)
1936 if (IS_ENABLED(CONFIG_MEMCG))
1937 call_rcu(&tsk->rcu, __delayed_free_task);
1942 static void copy_oom_score_adj(u64 clone_flags, struct task_struct *tsk)
1944 /* Skip if kernel thread */
1948 /* Skip if spawning a thread or using vfork */
1949 if ((clone_flags & (CLONE_VM | CLONE_THREAD | CLONE_VFORK)) != CLONE_VM)
1952 /* We need to synchronize with __set_oom_adj */
1953 mutex_lock(&oom_adj_mutex);
1954 set_bit(MMF_MULTIPROCESS, &tsk->mm->flags);
1955 /* Update the values in case they were changed after copy_signal */
1956 tsk->signal->oom_score_adj = current->signal->oom_score_adj;
1957 tsk->signal->oom_score_adj_min = current->signal->oom_score_adj_min;
1958 mutex_unlock(&oom_adj_mutex);
1962 * This creates a new process as a copy of the old one,
1963 * but does not actually start it yet.
1965 * It copies the registers, and all the appropriate
1966 * parts of the process environment (as per the clone
1967 * flags). The actual kick-off is left to the caller.
1969 static __latent_entropy struct task_struct *copy_process(
1973 struct kernel_clone_args *args)
1975 int pidfd = -1, retval;
1976 struct task_struct *p;
1977 struct multiprocess_signals delayed;
1978 struct file *pidfile = NULL;
1979 u64 clone_flags = args->flags;
1980 struct nsproxy *nsp = current->nsproxy;
1983 * Don't allow sharing the root directory with processes in a different
1986 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1987 return ERR_PTR(-EINVAL);
1989 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1990 return ERR_PTR(-EINVAL);
1993 * Thread groups must share signals as well, and detached threads
1994 * can only be started up within the thread group.
1996 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1997 return ERR_PTR(-EINVAL);
2000 * Shared signal handlers imply shared VM. By way of the above,
2001 * thread groups also imply shared VM. Blocking this case allows
2002 * for various simplifications in other code.
2004 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
2005 return ERR_PTR(-EINVAL);
2008 * Siblings of global init remain as zombies on exit since they are
2009 * not reaped by their parent (swapper). To solve this and to avoid
2010 * multi-rooted process trees, prevent global and container-inits
2011 * from creating siblings.
2013 if ((clone_flags & CLONE_PARENT) &&
2014 current->signal->flags & SIGNAL_UNKILLABLE)
2015 return ERR_PTR(-EINVAL);
2018 * If the new process will be in a different pid or user namespace
2019 * do not allow it to share a thread group with the forking task.
2021 if (clone_flags & CLONE_THREAD) {
2022 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
2023 (task_active_pid_ns(current) != nsp->pid_ns_for_children))
2024 return ERR_PTR(-EINVAL);
2028 * If the new process will be in a different time namespace
2029 * do not allow it to share VM or a thread group with the forking task.
2031 if (clone_flags & (CLONE_THREAD | CLONE_VM)) {
2032 if (nsp->time_ns != nsp->time_ns_for_children)
2033 return ERR_PTR(-EINVAL);
2036 if (clone_flags & CLONE_PIDFD) {
2038 * - CLONE_DETACHED is blocked so that we can potentially
2039 * reuse it later for CLONE_PIDFD.
2040 * - CLONE_THREAD is blocked until someone really needs it.
2042 if (clone_flags & (CLONE_DETACHED | CLONE_THREAD))
2043 return ERR_PTR(-EINVAL);
2047 * Force any signals received before this point to be delivered
2048 * before the fork happens. Collect up signals sent to multiple
2049 * processes that happen during the fork and delay them so that
2050 * they appear to happen after the fork.
2052 sigemptyset(&delayed.signal);
2053 INIT_HLIST_NODE(&delayed.node);
2055 spin_lock_irq(¤t->sighand->siglock);
2056 if (!(clone_flags & CLONE_THREAD))
2057 hlist_add_head(&delayed.node, ¤t->signal->multiprocess);
2058 recalc_sigpending();
2059 spin_unlock_irq(¤t->sighand->siglock);
2060 retval = -ERESTARTNOINTR;
2061 if (task_sigpending(current))
2065 p = dup_task_struct(current, node);
2068 if (args->io_thread) {
2070 * Mark us an IO worker, and block any signal that isn't
2073 p->flags |= PF_IO_WORKER;
2074 siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
2077 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
2079 * Clear TID on mm_release()?
2081 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? args->child_tid : NULL;
2083 ftrace_graph_init_task(p);
2085 rt_mutex_init_task(p);
2087 lockdep_assert_irqs_enabled();
2088 #ifdef CONFIG_PROVE_LOCKING
2089 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
2091 retval = copy_creds(p, clone_flags);
2096 if (is_ucounts_overlimit(task_ucounts(p), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
2097 if (p->real_cred->user != INIT_USER &&
2098 !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
2099 goto bad_fork_cleanup_count;
2101 current->flags &= ~PF_NPROC_EXCEEDED;
2104 * If multiple threads are within copy_process(), then this check
2105 * triggers too late. This doesn't hurt, the check is only there
2106 * to stop root fork bombs.
2109 if (data_race(nr_threads >= max_threads))
2110 goto bad_fork_cleanup_count;
2112 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
2113 p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE | PF_NO_SETAFFINITY);
2114 p->flags |= PF_FORKNOEXEC;
2115 INIT_LIST_HEAD(&p->children);
2116 INIT_LIST_HEAD(&p->sibling);
2117 rcu_copy_process(p);
2118 p->vfork_done = NULL;
2119 spin_lock_init(&p->alloc_lock);
2121 init_sigpending(&p->pending);
2123 p->utime = p->stime = p->gtime = 0;
2124 #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
2125 p->utimescaled = p->stimescaled = 0;
2127 prev_cputime_init(&p->prev_cputime);
2129 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
2130 seqcount_init(&p->vtime.seqcount);
2131 p->vtime.starttime = 0;
2132 p->vtime.state = VTIME_INACTIVE;
2135 #ifdef CONFIG_IO_URING
2139 #if defined(SPLIT_RSS_COUNTING)
2140 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
2143 p->default_timer_slack_ns = current->timer_slack_ns;
2149 task_io_accounting_init(&p->ioac);
2150 acct_clear_integrals(p);
2152 posix_cputimers_init(&p->posix_cputimers);
2154 p->io_context = NULL;
2155 audit_set_context(p, NULL);
2157 if (p->flags & PF_KTHREAD) {
2158 if (!set_kthread_struct(p))
2159 goto bad_fork_cleanup_delayacct;
2162 p->mempolicy = mpol_dup(p->mempolicy);
2163 if (IS_ERR(p->mempolicy)) {
2164 retval = PTR_ERR(p->mempolicy);
2165 p->mempolicy = NULL;
2166 goto bad_fork_cleanup_delayacct;
2169 #ifdef CONFIG_CPUSETS
2170 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
2171 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
2172 seqcount_spinlock_init(&p->mems_allowed_seq, &p->alloc_lock);
2174 #ifdef CONFIG_TRACE_IRQFLAGS
2175 memset(&p->irqtrace, 0, sizeof(p->irqtrace));
2176 p->irqtrace.hardirq_disable_ip = _THIS_IP_;
2177 p->irqtrace.softirq_enable_ip = _THIS_IP_;
2178 p->softirqs_enabled = 1;
2179 p->softirq_context = 0;
2182 p->pagefault_disabled = 0;
2184 #ifdef CONFIG_LOCKDEP
2185 lockdep_init_task(p);
2188 #ifdef CONFIG_DEBUG_MUTEXES
2189 p->blocked_on = NULL; /* not blocked yet */
2191 #ifdef CONFIG_BCACHE
2192 p->sequential_io = 0;
2193 p->sequential_io_avg = 0;
2195 #ifdef CONFIG_BPF_SYSCALL
2196 RCU_INIT_POINTER(p->bpf_storage, NULL);
2200 /* Perform scheduler related setup. Assign this task to a CPU. */
2201 retval = sched_fork(clone_flags, p);
2203 goto bad_fork_cleanup_policy;
2205 retval = perf_event_init_task(p, clone_flags);
2207 goto bad_fork_cleanup_policy;
2208 retval = audit_alloc(p);
2210 goto bad_fork_cleanup_perf;
2211 /* copy all the process information */
2213 retval = security_task_alloc(p, clone_flags);
2215 goto bad_fork_cleanup_audit;
2216 retval = copy_semundo(clone_flags, p);
2218 goto bad_fork_cleanup_security;
2219 retval = copy_files(clone_flags, p);
2221 goto bad_fork_cleanup_semundo;
2222 retval = copy_fs(clone_flags, p);
2224 goto bad_fork_cleanup_files;
2225 retval = copy_sighand(clone_flags, p);
2227 goto bad_fork_cleanup_fs;
2228 retval = copy_signal(clone_flags, p);
2230 goto bad_fork_cleanup_sighand;
2231 retval = copy_mm(clone_flags, p);
2233 goto bad_fork_cleanup_signal;
2234 retval = copy_namespaces(clone_flags, p);
2236 goto bad_fork_cleanup_mm;
2237 retval = copy_io(clone_flags, p);
2239 goto bad_fork_cleanup_namespaces;
2240 retval = copy_thread(clone_flags, args->stack, args->stack_size, p, args->tls);
2242 goto bad_fork_cleanup_io;
2244 stackleak_task_init(p);
2246 if (pid != &init_struct_pid) {
2247 pid = alloc_pid(p->nsproxy->pid_ns_for_children, args->set_tid,
2248 args->set_tid_size);
2250 retval = PTR_ERR(pid);
2251 goto bad_fork_cleanup_thread;
2256 * This has to happen after we've potentially unshared the file
2257 * descriptor table (so that the pidfd doesn't leak into the child
2258 * if the fd table isn't shared).
2260 if (clone_flags & CLONE_PIDFD) {
2261 retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
2263 goto bad_fork_free_pid;
2267 pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
2268 O_RDWR | O_CLOEXEC);
2269 if (IS_ERR(pidfile)) {
2270 put_unused_fd(pidfd);
2271 retval = PTR_ERR(pidfile);
2272 goto bad_fork_free_pid;
2274 get_pid(pid); /* held by pidfile now */
2276 retval = put_user(pidfd, args->pidfd);
2278 goto bad_fork_put_pidfd;
2287 * sigaltstack should be cleared when sharing the same VM
2289 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
2293 * Syscall tracing and stepping should be turned off in the
2294 * child regardless of CLONE_PTRACE.
2296 user_disable_single_step(p);
2297 clear_task_syscall_work(p, SYSCALL_TRACE);
2298 #if defined(CONFIG_GENERIC_ENTRY) || defined(TIF_SYSCALL_EMU)
2299 clear_task_syscall_work(p, SYSCALL_EMU);
2301 clear_tsk_latency_tracing(p);
2303 /* ok, now we should be set up.. */
2304 p->pid = pid_nr(pid);
2305 if (clone_flags & CLONE_THREAD) {
2306 p->group_leader = current->group_leader;
2307 p->tgid = current->tgid;
2309 p->group_leader = p;
2314 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
2315 p->dirty_paused_when = 0;
2317 p->pdeath_signal = 0;
2318 INIT_LIST_HEAD(&p->thread_group);
2319 p->task_works = NULL;
2320 clear_posix_cputimers_work(p);
2322 #ifdef CONFIG_KRETPROBES
2323 p->kretprobe_instances.first = NULL;
2327 * Ensure that the cgroup subsystem policies allow the new process to be
2328 * forked. It should be noted that the new process's css_set can be changed
2329 * between here and cgroup_post_fork() if an organisation operation is in
2332 retval = cgroup_can_fork(p, args);
2334 goto bad_fork_put_pidfd;
2337 * Now that the cgroups are pinned, re-clone the parent cgroup and put
2338 * the new task on the correct runqueue. All this *before* the task
2341 * This isn't part of ->can_fork() because while the re-cloning is
2342 * cgroup specific, it unconditionally needs to place the task on a
2345 sched_cgroup_fork(p, args);
2348 * From this point on we must avoid any synchronous user-space
2349 * communication until we take the tasklist-lock. In particular, we do
2350 * not want user-space to be able to predict the process start-time by
2351 * stalling fork(2) after we recorded the start_time but before it is
2352 * visible to the system.
2355 p->start_time = ktime_get_ns();
2356 p->start_boottime = ktime_get_boottime_ns();
2359 * Make it visible to the rest of the system, but dont wake it up yet.
2360 * Need tasklist lock for parent etc handling!
2362 write_lock_irq(&tasklist_lock);
2364 /* CLONE_PARENT re-uses the old parent */
2365 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
2366 p->real_parent = current->real_parent;
2367 p->parent_exec_id = current->parent_exec_id;
2368 if (clone_flags & CLONE_THREAD)
2369 p->exit_signal = -1;
2371 p->exit_signal = current->group_leader->exit_signal;
2373 p->real_parent = current;
2374 p->parent_exec_id = current->self_exec_id;
2375 p->exit_signal = args->exit_signal;
2378 klp_copy_process(p);
2382 spin_lock(¤t->sighand->siglock);
2385 * Copy seccomp details explicitly here, in case they were changed
2386 * before holding sighand lock.
2390 rseq_fork(p, clone_flags);
2392 /* Don't start children in a dying pid namespace */
2393 if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
2395 goto bad_fork_cancel_cgroup;
2398 /* Let kill terminate clone/fork in the middle */
2399 if (fatal_signal_pending(current)) {
2401 goto bad_fork_cancel_cgroup;
2404 init_task_pid_links(p);
2405 if (likely(p->pid)) {
2406 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
2408 init_task_pid(p, PIDTYPE_PID, pid);
2409 if (thread_group_leader(p)) {
2410 init_task_pid(p, PIDTYPE_TGID, pid);
2411 init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
2412 init_task_pid(p, PIDTYPE_SID, task_session(current));
2414 if (is_child_reaper(pid)) {
2415 ns_of_pid(pid)->child_reaper = p;
2416 p->signal->flags |= SIGNAL_UNKILLABLE;
2418 p->signal->shared_pending.signal = delayed.signal;
2419 p->signal->tty = tty_kref_get(current->signal->tty);
2421 * Inherit has_child_subreaper flag under the same
2422 * tasklist_lock with adding child to the process tree
2423 * for propagate_has_child_subreaper optimization.
2425 p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
2426 p->real_parent->signal->is_child_subreaper;
2427 list_add_tail(&p->sibling, &p->real_parent->children);
2428 list_add_tail_rcu(&p->tasks, &init_task.tasks);
2429 attach_pid(p, PIDTYPE_TGID);
2430 attach_pid(p, PIDTYPE_PGID);
2431 attach_pid(p, PIDTYPE_SID);
2432 __this_cpu_inc(process_counts);
2434 current->signal->nr_threads++;
2435 atomic_inc(¤t->signal->live);
2436 refcount_inc(¤t->signal->sigcnt);
2437 task_join_group_stop(p);
2438 list_add_tail_rcu(&p->thread_group,
2439 &p->group_leader->thread_group);
2440 list_add_tail_rcu(&p->thread_node,
2441 &p->signal->thread_head);
2443 attach_pid(p, PIDTYPE_PID);
2447 hlist_del_init(&delayed.node);
2448 spin_unlock(¤t->sighand->siglock);
2449 syscall_tracepoint_update(p);
2450 write_unlock_irq(&tasklist_lock);
2453 fd_install(pidfd, pidfile);
2455 proc_fork_connector(p);
2457 cgroup_post_fork(p, args);
2460 trace_task_newtask(p, clone_flags);
2461 uprobe_copy_process(p, clone_flags);
2463 copy_oom_score_adj(clone_flags, p);
2467 bad_fork_cancel_cgroup:
2469 spin_unlock(¤t->sighand->siglock);
2470 write_unlock_irq(&tasklist_lock);
2471 cgroup_cancel_fork(p, args);
2473 if (clone_flags & CLONE_PIDFD) {
2475 put_unused_fd(pidfd);
2478 if (pid != &init_struct_pid)
2480 bad_fork_cleanup_thread:
2482 bad_fork_cleanup_io:
2485 bad_fork_cleanup_namespaces:
2486 exit_task_namespaces(p);
2487 bad_fork_cleanup_mm:
2489 mm_clear_owner(p->mm, p);
2492 bad_fork_cleanup_signal:
2493 if (!(clone_flags & CLONE_THREAD))
2494 free_signal_struct(p->signal);
2495 bad_fork_cleanup_sighand:
2496 __cleanup_sighand(p->sighand);
2497 bad_fork_cleanup_fs:
2498 exit_fs(p); /* blocking */
2499 bad_fork_cleanup_files:
2500 exit_files(p); /* blocking */
2501 bad_fork_cleanup_semundo:
2503 bad_fork_cleanup_security:
2504 security_task_free(p);
2505 bad_fork_cleanup_audit:
2507 bad_fork_cleanup_perf:
2508 perf_event_free_task(p);
2509 bad_fork_cleanup_policy:
2510 lockdep_free_task(p);
2512 mpol_put(p->mempolicy);
2514 bad_fork_cleanup_delayacct:
2515 delayacct_tsk_free(p);
2516 bad_fork_cleanup_count:
2517 dec_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
2520 WRITE_ONCE(p->__state, TASK_DEAD);
2521 exit_task_stack_account(p);
2523 delayed_free_task(p);
2525 spin_lock_irq(¤t->sighand->siglock);
2526 hlist_del_init(&delayed.node);
2527 spin_unlock_irq(¤t->sighand->siglock);
2528 return ERR_PTR(retval);
2531 static inline void init_idle_pids(struct task_struct *idle)
2535 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
2536 INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */
2537 init_task_pid(idle, type, &init_struct_pid);
2541 struct task_struct * __init fork_idle(int cpu)
2543 struct task_struct *task;
2544 struct kernel_clone_args args = {
2548 task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
2549 if (!IS_ERR(task)) {
2550 init_idle_pids(task);
2551 init_idle(task, cpu);
2557 struct mm_struct *copy_init_mm(void)
2559 return dup_mm(NULL, &init_mm);
2563 * This is like kernel_clone(), but shaved down and tailored to just
2564 * creating io_uring workers. It returns a created task, or an error pointer.
2565 * The returned task is inactive, and the caller must fire it up through
2566 * wake_up_new_task(p). All signals are blocked in the created task.
2568 struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
2570 unsigned long flags = CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|
2572 struct kernel_clone_args args = {
2573 .flags = ((lower_32_bits(flags) | CLONE_VM |
2574 CLONE_UNTRACED) & ~CSIGNAL),
2575 .exit_signal = (lower_32_bits(flags) & CSIGNAL),
2576 .stack = (unsigned long)fn,
2577 .stack_size = (unsigned long)arg,
2581 return copy_process(NULL, 0, node, &args);
2585 * Ok, this is the main fork-routine.
2587 * It copies the process, and if successful kick-starts
2588 * it and waits for it to finish using the VM if required.
2590 * args->exit_signal is expected to be checked for sanity by the caller.
2592 pid_t kernel_clone(struct kernel_clone_args *args)
2594 u64 clone_flags = args->flags;
2595 struct completion vfork;
2597 struct task_struct *p;
2602 * For legacy clone() calls, CLONE_PIDFD uses the parent_tid argument
2603 * to return the pidfd. Hence, CLONE_PIDFD and CLONE_PARENT_SETTID are
2604 * mutually exclusive. With clone3() CLONE_PIDFD has grown a separate
2605 * field in struct clone_args and it still doesn't make sense to have
2606 * them both point at the same memory location. Performing this check
2607 * here has the advantage that we don't need to have a separate helper
2608 * to check for legacy clone().
2610 if ((args->flags & CLONE_PIDFD) &&
2611 (args->flags & CLONE_PARENT_SETTID) &&
2612 (args->pidfd == args->parent_tid))
2616 * Determine whether and which event to report to ptracer. When
2617 * called from kernel_thread or CLONE_UNTRACED is explicitly
2618 * requested, no event is reported; otherwise, report if the event
2619 * for the type of forking is enabled.
2621 if (!(clone_flags & CLONE_UNTRACED)) {
2622 if (clone_flags & CLONE_VFORK)
2623 trace = PTRACE_EVENT_VFORK;
2624 else if (args->exit_signal != SIGCHLD)
2625 trace = PTRACE_EVENT_CLONE;
2627 trace = PTRACE_EVENT_FORK;
2629 if (likely(!ptrace_event_enabled(current, trace)))
2633 p = copy_process(NULL, trace, NUMA_NO_NODE, args);
2634 add_latent_entropy();
2640 * Do this prior waking up the new thread - the thread pointer
2641 * might get invalid after that point, if the thread exits quickly.
2643 trace_sched_process_fork(current, p);
2645 pid = get_task_pid(p, PIDTYPE_PID);
2648 if (clone_flags & CLONE_PARENT_SETTID)
2649 put_user(nr, args->parent_tid);
2651 if (clone_flags & CLONE_VFORK) {
2652 p->vfork_done = &vfork;
2653 init_completion(&vfork);
2657 wake_up_new_task(p);
2659 /* forking complete and child started to run, tell ptracer */
2660 if (unlikely(trace))
2661 ptrace_event_pid(trace, pid);
2663 if (clone_flags & CLONE_VFORK) {
2664 if (!wait_for_vfork_done(p, &vfork))
2665 ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
2673 * Create a kernel thread.
2675 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
2677 struct kernel_clone_args args = {
2678 .flags = ((lower_32_bits(flags) | CLONE_VM |
2679 CLONE_UNTRACED) & ~CSIGNAL),
2680 .exit_signal = (lower_32_bits(flags) & CSIGNAL),
2681 .stack = (unsigned long)fn,
2682 .stack_size = (unsigned long)arg,
2685 return kernel_clone(&args);
2688 #ifdef __ARCH_WANT_SYS_FORK
2689 SYSCALL_DEFINE0(fork)
2692 struct kernel_clone_args args = {
2693 .exit_signal = SIGCHLD,
2696 return kernel_clone(&args);
2698 /* can not support in nommu mode */
2704 #ifdef __ARCH_WANT_SYS_VFORK
2705 SYSCALL_DEFINE0(vfork)
2707 struct kernel_clone_args args = {
2708 .flags = CLONE_VFORK | CLONE_VM,
2709 .exit_signal = SIGCHLD,
2712 return kernel_clone(&args);
2716 #ifdef __ARCH_WANT_SYS_CLONE
2717 #ifdef CONFIG_CLONE_BACKWARDS
2718 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2719 int __user *, parent_tidptr,
2721 int __user *, child_tidptr)
2722 #elif defined(CONFIG_CLONE_BACKWARDS2)
2723 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
2724 int __user *, parent_tidptr,
2725 int __user *, child_tidptr,
2727 #elif defined(CONFIG_CLONE_BACKWARDS3)
2728 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
2730 int __user *, parent_tidptr,
2731 int __user *, child_tidptr,
2734 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
2735 int __user *, parent_tidptr,
2736 int __user *, child_tidptr,
2740 struct kernel_clone_args args = {
2741 .flags = (lower_32_bits(clone_flags) & ~CSIGNAL),
2742 .pidfd = parent_tidptr,
2743 .child_tid = child_tidptr,
2744 .parent_tid = parent_tidptr,
2745 .exit_signal = (lower_32_bits(clone_flags) & CSIGNAL),
2750 return kernel_clone(&args);
2754 #ifdef __ARCH_WANT_SYS_CLONE3
2756 noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
2757 struct clone_args __user *uargs,
2761 struct clone_args args;
2762 pid_t *kset_tid = kargs->set_tid;
2764 BUILD_BUG_ON(offsetofend(struct clone_args, tls) !=
2765 CLONE_ARGS_SIZE_VER0);
2766 BUILD_BUG_ON(offsetofend(struct clone_args, set_tid_size) !=
2767 CLONE_ARGS_SIZE_VER1);
2768 BUILD_BUG_ON(offsetofend(struct clone_args, cgroup) !=
2769 CLONE_ARGS_SIZE_VER2);
2770 BUILD_BUG_ON(sizeof(struct clone_args) != CLONE_ARGS_SIZE_VER2);
2772 if (unlikely(usize > PAGE_SIZE))
2774 if (unlikely(usize < CLONE_ARGS_SIZE_VER0))
2777 err = copy_struct_from_user(&args, sizeof(args), uargs, usize);
2781 if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
2784 if (unlikely(!args.set_tid && args.set_tid_size > 0))
2787 if (unlikely(args.set_tid && args.set_tid_size == 0))
2791 * Verify that higher 32bits of exit_signal are unset and that
2792 * it is a valid signal
2794 if (unlikely((args.exit_signal & ~((u64)CSIGNAL)) ||
2795 !valid_signal(args.exit_signal)))
2798 if ((args.flags & CLONE_INTO_CGROUP) &&
2799 (args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2))
2802 *kargs = (struct kernel_clone_args){
2803 .flags = args.flags,
2804 .pidfd = u64_to_user_ptr(args.pidfd),
2805 .child_tid = u64_to_user_ptr(args.child_tid),
2806 .parent_tid = u64_to_user_ptr(args.parent_tid),
2807 .exit_signal = args.exit_signal,
2808 .stack = args.stack,
2809 .stack_size = args.stack_size,
2811 .set_tid_size = args.set_tid_size,
2812 .cgroup = args.cgroup,
2816 copy_from_user(kset_tid, u64_to_user_ptr(args.set_tid),
2817 (kargs->set_tid_size * sizeof(pid_t))))
2820 kargs->set_tid = kset_tid;
2826 * clone3_stack_valid - check and prepare stack
2827 * @kargs: kernel clone args
2829 * Verify that the stack arguments userspace gave us are sane.
2830 * In addition, set the stack direction for userspace since it's easy for us to
2833 static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
2835 if (kargs->stack == 0) {
2836 if (kargs->stack_size > 0)
2839 if (kargs->stack_size == 0)
2842 if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
2845 #if !defined(CONFIG_STACK_GROWSUP) && !defined(CONFIG_IA64)
2846 kargs->stack += kargs->stack_size;
2853 static bool clone3_args_valid(struct kernel_clone_args *kargs)
2855 /* Verify that no unknown flags are passed along. */
2857 ~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP))
2861 * - make the CLONE_DETACHED bit reusable for clone3
2862 * - make the CSIGNAL bits reusable for clone3
2864 if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
2867 if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
2868 (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND))
2871 if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
2875 if (!clone3_stack_valid(kargs))
2882 * clone3 - create a new process with specific properties
2883 * @uargs: argument structure
2884 * @size: size of @uargs
2886 * clone3() is the extensible successor to clone()/clone2().
2887 * It takes a struct as argument that is versioned by its size.
2889 * Return: On success, a positive PID for the child process.
2890 * On error, a negative errno number.
2892 SYSCALL_DEFINE2(clone3, struct clone_args __user *, uargs, size_t, size)
2896 struct kernel_clone_args kargs;
2897 pid_t set_tid[MAX_PID_NS_LEVEL];
2899 kargs.set_tid = set_tid;
2901 err = copy_clone_args_from_user(&kargs, uargs, size);
2905 if (!clone3_args_valid(&kargs))
2908 return kernel_clone(&kargs);
2912 void walk_process_tree(struct task_struct *top, proc_visitor visitor, void *data)
2914 struct task_struct *leader, *parent, *child;
2917 read_lock(&tasklist_lock);
2918 leader = top = top->group_leader;
2920 for_each_thread(leader, parent) {
2921 list_for_each_entry(child, &parent->children, sibling) {
2922 res = visitor(child, data);
2934 if (leader != top) {
2936 parent = child->real_parent;
2937 leader = parent->group_leader;
2941 read_unlock(&tasklist_lock);
2944 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
2945 #define ARCH_MIN_MMSTRUCT_ALIGN 0
2948 static void sighand_ctor(void *data)
2950 struct sighand_struct *sighand = data;
2952 spin_lock_init(&sighand->siglock);
2953 init_waitqueue_head(&sighand->signalfd_wqh);
2956 void __init proc_caches_init(void)
2958 unsigned int mm_size;
2960 sighand_cachep = kmem_cache_create("sighand_cache",
2961 sizeof(struct sighand_struct), 0,
2962 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
2963 SLAB_ACCOUNT, sighand_ctor);
2964 signal_cachep = kmem_cache_create("signal_cache",
2965 sizeof(struct signal_struct), 0,
2966 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2968 files_cachep = kmem_cache_create("files_cache",
2969 sizeof(struct files_struct), 0,
2970 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2972 fs_cachep = kmem_cache_create("fs_cache",
2973 sizeof(struct fs_struct), 0,
2974 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2978 * The mm_cpumask is located at the end of mm_struct, and is
2979 * dynamically sized based on the maximum CPU number this system
2980 * can have, taking hotplug into account (nr_cpu_ids).
2982 mm_size = sizeof(struct mm_struct) + cpumask_size();
2984 mm_cachep = kmem_cache_create_usercopy("mm_struct",
2985 mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
2986 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
2987 offsetof(struct mm_struct, saved_auxv),
2988 sizeof_field(struct mm_struct, saved_auxv),
2990 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
2992 nsproxy_cache_init();
2996 * Check constraints on flags passed to the unshare system call.
2998 static int check_unshare_flags(unsigned long unshare_flags)
3000 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
3001 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
3002 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
3003 CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWCGROUP|
3007 * Not implemented, but pretend it works if there is nothing
3008 * to unshare. Note that unsharing the address space or the
3009 * signal handlers also need to unshare the signal queues (aka
3012 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
3013 if (!thread_group_empty(current))
3016 if (unshare_flags & (CLONE_SIGHAND | CLONE_VM)) {
3017 if (refcount_read(¤t->sighand->count) > 1)
3020 if (unshare_flags & CLONE_VM) {
3021 if (!current_is_single_threaded())
3029 * Unshare the filesystem structure if it is being shared
3031 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
3033 struct fs_struct *fs = current->fs;
3035 if (!(unshare_flags & CLONE_FS) || !fs)
3038 /* don't need lock here; in the worst case we'll do useless copy */
3042 *new_fsp = copy_fs_struct(fs);
3050 * Unshare file descriptor table if it is being shared
3052 int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
3053 struct files_struct **new_fdp)
3055 struct files_struct *fd = current->files;
3058 if ((unshare_flags & CLONE_FILES) &&
3059 (fd && atomic_read(&fd->count) > 1)) {
3060 *new_fdp = dup_fd(fd, max_fds, &error);
3069 * unshare allows a process to 'unshare' part of the process
3070 * context which was originally shared using clone. copy_*
3071 * functions used by kernel_clone() cannot be used here directly
3072 * because they modify an inactive task_struct that is being
3073 * constructed. Here we are modifying the current, active,
3076 int ksys_unshare(unsigned long unshare_flags)
3078 struct fs_struct *fs, *new_fs = NULL;
3079 struct files_struct *new_fd = NULL;
3080 struct cred *new_cred = NULL;
3081 struct nsproxy *new_nsproxy = NULL;
3086 * If unsharing a user namespace must also unshare the thread group
3087 * and unshare the filesystem root and working directories.
3089 if (unshare_flags & CLONE_NEWUSER)
3090 unshare_flags |= CLONE_THREAD | CLONE_FS;
3092 * If unsharing vm, must also unshare signal handlers.
3094 if (unshare_flags & CLONE_VM)
3095 unshare_flags |= CLONE_SIGHAND;
3097 * If unsharing a signal handlers, must also unshare the signal queues.
3099 if (unshare_flags & CLONE_SIGHAND)
3100 unshare_flags |= CLONE_THREAD;
3102 * If unsharing namespace, must also unshare filesystem information.
3104 if (unshare_flags & CLONE_NEWNS)
3105 unshare_flags |= CLONE_FS;
3107 err = check_unshare_flags(unshare_flags);
3109 goto bad_unshare_out;
3111 * CLONE_NEWIPC must also detach from the undolist: after switching
3112 * to a new ipc namespace, the semaphore arrays from the old
3113 * namespace are unreachable.
3115 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
3117 err = unshare_fs(unshare_flags, &new_fs);
3119 goto bad_unshare_out;
3120 err = unshare_fd(unshare_flags, NR_OPEN_MAX, &new_fd);
3122 goto bad_unshare_cleanup_fs;
3123 err = unshare_userns(unshare_flags, &new_cred);
3125 goto bad_unshare_cleanup_fd;
3126 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
3129 goto bad_unshare_cleanup_cred;
3132 err = set_cred_ucounts(new_cred);
3134 goto bad_unshare_cleanup_cred;
3137 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
3140 * CLONE_SYSVSEM is equivalent to sys_exit().
3144 if (unshare_flags & CLONE_NEWIPC) {
3145 /* Orphan segments in old ns (see sem above). */
3147 shm_init_task(current);
3151 switch_task_namespaces(current, new_nsproxy);
3157 spin_lock(&fs->lock);
3158 current->fs = new_fs;
3163 spin_unlock(&fs->lock);
3167 swap(current->files, new_fd);
3169 task_unlock(current);
3172 /* Install the new user namespace */
3173 commit_creds(new_cred);
3178 perf_event_namespaces(current);
3180 bad_unshare_cleanup_cred:
3183 bad_unshare_cleanup_fd:
3185 put_files_struct(new_fd);
3187 bad_unshare_cleanup_fs:
3189 free_fs_struct(new_fs);
3195 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
3197 return ksys_unshare(unshare_flags);
3201 * Helper to unshare the files of the current task.
3202 * We don't want to expose copy_files internals to
3203 * the exec layer of the kernel.
3206 int unshare_files(void)
3208 struct task_struct *task = current;
3209 struct files_struct *old, *copy = NULL;
3212 error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, ©);
3220 put_files_struct(old);
3224 int sysctl_max_threads(struct ctl_table *table, int write,
3225 void *buffer, size_t *lenp, loff_t *ppos)
3229 int threads = max_threads;
3231 int max = MAX_THREADS;
3238 ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
3242 max_threads = threads;